Epoxy-Reactive Battery Separator Coating for Gel Electrolyte Adhesion
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Solution Overview
Problem
Conventional lithium secondary batteries using liquid electrolytes face safety issues due to degradation and combustion risks, while solid polymer electrolytes have poor performance, and existing gel polymer electrolyte separation membranes lack adequate adhesion, leading to interfacial resistance and short-circuits.
Innovation Solution
A separation membrane with a multi-layer structure, comprising a substrate, a first coating layer with a substituted polyvinylidene fluoride binder, and a second coating layer with an inorganic oxide, enhancing adhesion with the gel polymer electrolyte through epoxy ring-opening reactions, improving bonding and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a liquid electrolyte is used in the lithium secondary battery, then the battery performance is improved, but the safety deteriorates due to degradation and combustion risks
Solution Approach 1:
The patent uses a composite gel polymer electrolyte combining polyacrylonitrile polymer matrix with cyclic carbonate and chain carbonate solvents, creating a material that exhibits both gel and liquid electrolyte characteristics. This composite structure provides the high ionic conductivity of liquid electrolytes while maintaining the safety and structural stability of gel electrolytes, preventing combustion and degradation issues
Solution Approach 2:
The patent modifies the physical and chemical parameters of the electrolyte by controlling the gel fraction (30-80%), the ratio of cyclic to chain carbonate solvents, and the molecular weight of the polymer. These parameter adjustments optimize the balance between ionic conductivity (performance) and structural integrity (safety), allowing the electrolyte to function effectively while preventing thermal runaway
2Reliability
If a solid polymer electrolyte is used to improve safety, then the reliability is improved, but the battery performance deteriorates
Solution Approach 1:
The patent adjusts critical parameters including the gel fraction (30-80%), polymer molecular weight (10,000-1,000,000), and solvent ratios to optimize performance. By controlling these parameters, the electrolyte achieves high ionic conductivity (approaching liquid electrolyte levels) while maintaining the structural stability and safety of solid polymer electrolytes
Solution Approach 2:
The patent creates a composite gel polymer electrolyte that integrates the advantages of both solid and liquid electrolytes. The polyacrylonitrile polymer matrix provides structural integrity and safety, while the cyclic and chain carbonate solvents provide high ionic conductivity, achieving a balance between safety and performance
3Ease of manufacture
If a conventional separation membrane is used, then the manufacturing simplicity is maintained, but the adhesion with gel polymer electrolyte deteriorates leading to interfacial resistance
Solution Approach 1:
The patent applies a coating layer with specific local properties (containing carboxyl, hydroxyl, or amine functional groups) only on the surface of the separation membrane. This localized modification provides excellent adhesion to the gel polymer electrolyte at the interface while maintaining the simple polyolefin structure and manufacturing process of the bulk membrane material
4Reliability
If the separation membrane thickness is increased to prevent short-circuits, then the safety is improved, but the battery energy density deteriorates
Solution Approach 1:
The patent concentrates the safety-enhancing features (adhesion promotion, short-circuit prevention) in a thin coating layer on the membrane surface rather than increasing the overall membrane thickness. The functional coating provides excellent adhesion and electrochemical stability, allowing the use of thin-film separation membranes that maintain high energy density while ensuring safety
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enhances the bonding force between the gel polymer electrolyte and the separation membrane, preventing short-circuits and improving the safety and lifespan of lithium secondary batteries by maintaining a constant thickness and stability.
Implementation Method 1
a first coating layer containing a first organic binder which is able to be bonded to a gel polymer electrolyte through an epoxy ring-opening reaction
Data Source
Figure 1~2
AI summary
The present invention provides a separation membrane for a lithium secondary battery and a lithium secondary battery including the same, the separation membrane including: a substrate; a first coating layer containing a first organic binder which is able to be bonded to a gel polymer electrolyte through an epoxy ring-opening reaction; and a second coating layer containing a second organic binder, wherein the first organic binder has a functional group capable of ring-opening reaction with an epoxy group, or a combination thereof, and the gel polymer electrolyte is formed by polymerizing an oligomer having an epoxy group, a functional group capable of ring-opening reaction with an epoxy group, or a combination thereof.